Minium, or Red Lead

a lead oxide mineral from the southwestern United States

Above:
A west- to -east section looking north through the Leadville
district, 8.6 km long, from Emmons (1882).

Two small samples in my collection are:

a) sample 1442, minium with jarosite from Leadville, Lake county,
Colorado (ex-David New). Brilliant red minium with grey quartz and
bright yellow jarosite. This little sample is just 40x35x23 mm in maximum
dimensions but feels very dense at 51.41 grams: there is relict
fine-grained granular galena within the oxide.
The jarosite is late, in veinlets that crosscut both the primary ore
and the secondary Pb oxide. The sample is not appreciably magnetic,
bulk magnetic susceptibility <0.03x10-3 SI units.

and

b) BELOW: two complementary views of sample 1885, minium on cerussite, from the Tonopah-Belmont mine,
Maricopa county, in west-central Arizona (ex-David Shannon). Dense, pale brownish
cerussite
with minor malachite and perhaps other green Cu salts,
invested with powdery bright orange minium.
The sample weighs 48.92 grams, is a maximum of 53x35x20 mm in size,
and displays magnetic susceptibility <0.02x10-3 SI units.
The sample has a solid heft for its size,
and the interior is likely an altered
Tertiary volcanic rock of (?) andesitic composition.
The mine's geology and mineralogy are described by Allen and Hunt (1988).
Minium, as a secondary salt, formed near the end of the paragenesis,
the sequence of crystallization of minerals, that began with primary
sulphides such as galena (PbS), chalcopyrite and sphalerite,
plus gold and silver as native elements.
The late secondary minerals include minium, calcite, gypsum and hydrozincite.
Minium is reported to form bright red pseudomorphs after cerussite
(PbCO3)
on willemite (a zinc silicate), but the material
shown here appears to be the more typical late crust.

"Rock of the Month #113, posted for November 2010" ---

Minium, better known as red lead is a seldom-recognized
lead oxide mineral, formula
Pb2+2Pb4+O4,
also obscurely known as miniumite
or minio (Clark, 1993, p.461). Long ago the name minium was applied
to a more famous red mineral, cinnabar, the lead oxide being an adulterant
in the mercury sulphide (Blackburn and Dennen, 1997,
p.200).
Related phases include two polymorphs of PbO, massicot and
litharge. It is said (Pough, 1996, pp.144-145) that masses of
minium at Broken Hill, New South Wales, Australia, formed by
the roasting of cerussite ore, may be some of the best material
available, albeit a "man-made mineral", not exactly nature's
own...

Minium is most often found in lead deposits with abundant secondary,
oxidized mineral species. Examples are Leadville, Colorado (Emmons,
1882), the South Mountain district of Idaho (Sorensen, 1927), and
Ojuela, Durango (Moore and Megaw, 2003).
Panczner (1987) provides a short list of minium occurrences
in 7 states of Mexico, including
the Lomo del Toro mine in Zimapan, Hidalgo.

In the Leadville mining camp, the principal ore mineral in the
early days was argentiferous galena, supplemented by
cerargyrite, anglesite and cerussite,
plus pyromorphite, litharge, minium and other minerals (Emmons, 1882).

Minium has also been reported from other base-metal mining areas,
including Tintic, Utah (Tower and Smith, 1899) and Parys Mountain
in Wales (Plant et al., 2011).
Minium has also been found in slags and related wastes of the Laurium
(Laurion) mines of Greece (Mishara, 1989; Gelaude et al.,
1996). Another ancient mining site which is a minium occurrence is
Kuhne Mes in southern Iran (Haynes, 1989).
Although uncommon, it is described in a number of popular
mineralogy texts, such as Pough (1970) and Bauer and Tvrz (1974).

Little recent research seems to have been done, though
McConachy et al. (2007) include minium in a cataloguing
of spectral reflectance data, with potential for the exploration for
oxidized (non-sulphide) base-metal deposits.